Short in the Tahoe 2003 LT

I have a short somewhere in the system. My guy hooked his machine to my charging unit and there was a 20 amp drain every two min or so. I have to diconnect my battery every night. Any ideas on what this could be. I have a 2003 Tahoe LT with autoride and 159,455KM. The Battery is new. Thanks in advance...Eric